Method and instrumentation for unicompartmental total knee arthroplasty

ABSTRACT

A method and instruments for replacing the articulating surfaces of a knee joint in which the diseased area is restricted to one of the medial and lateral compartments. A femoral intramedullary rod is placed down the center of the femur. A femoral cutting block is affixed at one side to the rod and at the other side to an outrigger attached to the femur by smooth pins. The cutting block is adjustable rotationally and in the anterior-posterior plane. The cutting block is provided with surgical saw guide slots for the posterior and distal articular surface cuts and the chamfer cuts, all of which are made with the cutting block in place. The cutting block is removed and a drill guide is used for drilling two holes in the distal articular cut surface for receipt of the mounting pegs of the femoral unicompartmental prosthetic implant. A tibial intramedullary rod is placed down the center of the tibia, to which is adjustably affixed a vertical cutting block, a horizontal cutting guide and a caliper measuring device. The caliper measuring device is used to properly locate the cutting guide and the horizontal tibial cut is made. Upon removal of the measuring device and cutting guide, the cutting block is used to guide the vertical cut. The cutting block and tibial intramedullary rod are removed. The tibial prosthesis comprises a tray and a snap-in bearing insert. A tibial template is placed on the horizontal tibial cut surface and a hole for the tray mounting peg is drilled together with additional holes for mounting screws, if used.

TECHNICAL FIELD

The invention relates to unicompartmental total knee arthroplasty, andmore particularly to an improved method and improved instrumentationtherefor.

BACKGROUND ART

The present invention is directed to the replacement of the articulatingsurfaces of a knee joint in which the diseased area is restricted toeither the medial or the lateral compartment, not both, and which stillmaintains good ligamentous stability. As compared to tricompartmentaltotal knee arthroplasty, unicompartmental total knee arthroplasty, whenits use is indicated, has a number of advantages. These advantagesinclude less hospitalization, decreased blood loss, increased range ofmotion, and decreased pain.

Prior art workers have devised a number of procedures inunicompartmental total knee arthroplasty. The accuracy andreproducibility of the associated femoral and tibial cuts forpreparation of the femur and tibia to receive their respectiveprostheses has long been a major concern to the orthopaedic surgeon.Prior art procedures and instruments require the serial fixation,removal and replacement of numerous cutting blocks to prepare the bone,basing secondary cuts on the not-so-inherent accuracy of the initialcuts.

The present invention is based upon the development of a method andinstrumentation which allow the surgeon to complete all of the femoraland tibial cuts with one guide assembly for each. Both the femoral andthe tibial guide assemblies are firmly affixed and are left intact untilall the cuts have been completed, while still maintaining theversatility required for proper positioning.

The surgical procedure followed for preparing the distal femur bases thecuts on the affected condyle only, and does not disturb the unaffectedside in any manner. Fixation of the single femoral cutting guide blockis achieved utilizing the diseased side only.

The method and instrumentation of the present invention enables the useof a conventional femoral prosthesis having a pair of mounting pegs anda tibial prosthesis which comprises a tibial tray having anteriorly andposteriorly placed locking lips which engage the flexible tabs on thecorresponding sides of a removable plastic bearing insert. The bearinginsert is available in multiple thicknesses and both the tray and theinsert are provided in left and right configurations. The tibial trayincludes a rigidly affixed, posteriorly angled peg. According to thepresent invention, the tray also includes a medial and an anterior holefor screws by which it may be additionally affixed to the tibia. Theposteriorly angled peg in conjunction with the screws provides divergentforces on the tibia to keep the tray firmly fixed. The femoral andtibial prostheses may also be affixed by an appropriate bone adhesive.The holes in the tibial tray for the mounting screws may be plugged withplastic inserts, when the mounting screws are not used.

In the preparation of the distal femur, a single cutting block is used.The cutting block is adjustable in the anterior-posterior plane androtationally, and is firmly affixed to the femur by a femoralintramedullary rod on one side of the cutting block and an outriggerassembly on the other side of the cutting block, which is attacheddirectly to the femur by a pair of smooth pins. The cutting block isprovided with surgical saw guide slots for the posterior articularsurface cut, the distal articular surface cut, and the chamfer cuts. Allof these cuts are made with the single cutting block mounted in place.These four cuts can be made in any order. The cutting block can be usedfor resection of either the medial condylar surface or the lateralcondylar surface by reversing the positions of the femoralintramedullary rod and the outrigger.

The surgical procedure followed for preparing the proximal tibiautilizes an intramedullary rod to which all components of the tibialcutting guide assembly are adjustably affixed. The tibial guide assemblyincludes a horizontal cutting guide which can be rotated about theintramedullary rod and shifted in all radial directions to facilitateproper positioning thereof against the anterior tibial surface on theoperative side. The tibial guide assembly also includes a calipermeasuring device to assist in the location of the horizontal cuttingguide.

The tibial cutting guide assembly additionally includes a verticalcutting block, available in various widths, to guide the surgical sawduring the vertical tibial cut.

The tibial cutting guide assembly for making both tibial plateau cutscan be used regardless of component sizing and with either compartment.

DISCLOSURE OF THE INVENTION

According to the invention there is Provided both a method andinstrumentation for replacing the articulating surfaces of a knee jointin which the diseased area is restricted to either the medial or thelateral compartment. The method employs a conventional femoralunicompartmental prosthetic metallic implant having a pair of mountingpegs and a modular type tibial unicompartmental Prosthetic implantavailable in left and right configurations and comprising a metallictray having a posteriorly angled mounting peg and a removable plasticbearing insert available in multiple thicknesses and left and rightconfigurations.

A femoral intramedullary rod is placed down the center of the femur. Afemoral cutting block is affixed at one of its sides to the femoralintramedullary rod and at the other of its sides to an outrigger which,in turn, is attached to the femur by a pair of smooth pins. Theattachment of the femoral cutting block to the femoral intramedullaryrod and the outrigger is such as to permit adjustment rotationally andin the anterior-posterior plane and firm fixation in the finallyadjusted position. The cutting block is provided with surgical saw guideslots for the posterior and distal articular surface cuts and for thechamfer cuts. All four cuts are made with the cutting block in place.

After the femoral cuts are made, the femoral cutting block is removedand a drill guide is used for drilling two holes in the distal articularcut surface for the receipt of the mounting pegs of the femoralunicompartmental prosthetic implant.

A tibial intramedullary rod is placed down the center of the tibialcanal onto which is mounted a tibial cutting guide assembly. The tibialcutting guide assembly comprises a vertical tibial cutting block, ahorizontal tibial cutting guide and a caliper measuring device, allthree of which are mounted on the tibial intramedullary rod one, abovethe other, in the order named. The caliper measuring device is used toproperly locate the horizontal tibial cutting guide and the horizontaltibial cut is made. The caliper measuring device and the horizontaltibial cutting guide are thereafter removed from the tibialintramedullary rod, and the vertical tibial cutting block is then usedto guide the vertical tibial cut. With both tibial cuts performed, thevertical tibial cutting block and the tibial intramedullary rod areremoved from the tibia. A tibial template is placed on the horizontaltibial cut surface and a hole is drilled for the tibial tray mountingpeg. The tibial tray is provided with countersunk medial and anteriorholes to accommodate mounting screws, if used. The tibial template isprovided with guide holes so that pilot holes may be drilled for suchscrews. Once the tibial tray is mounted on the tibia, an appropriatelysized plastic bearing insert is mounted in the tray, with a snap fit.

Both the femoral implant and the tibial tray may be affixed in place bymeans of their mounting pegs and an appropriate adhesive. When this isdone, the tibial tray mounting screws might not be used, their pilotholes not drilled, and the mounting screw holes in the tibial trayfilled with plastic plugs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of the femoral template of the presentinvention.

FIG. 2 is an end view of the femoral template as seen from the right ofFIG. 1.

FIG. 3 is an elevational view of the femoral intramedullary rod of thepresent invention.

FIG. 4 is a top view of the intramedullary rod of FIG. 3.

FIG. 5 is a side elevational view of the femoral cutting guide locatorof the present invention.

FIG. 6 is an elevational view of the femoral cutting block of thepresent invention.

FIG. 7 is a side view of the femoral cutting block as seen from theright of FIG. 6.

FIG. 8 is an elevational view of the femoral outrigger of the presentinvention.

FIG. 9 is an edge view of the femoral outrigger as seen from the bottomof FIG. 8.

FIG. 10 is an exploded perspective view of the full femoral cuttingblock assembly of the present invention.

FIG. 11 is an elevational view of the femoral drill guide of the presentinvention.

FIG. 12 is an elevational view of the femoral intramedullary rod removalinstrument of the present invention.

FIG. 13 is a fragmentary elevational view illustrating the use of thefemoral template.

FIG. 14 is a fragmentary perspective view illustrating the drilling ofthe femur for the intramedullary rod.

FIG. 15 is a fragmentary elevational view illustrating placement of theintramedullary rod in the femur.

FIG. 16 is a fragmentary elevational view of the femoral cutting blockbolted in place.

FIG. 17 is a fragmentary perspective view illustrating the use of thefemoral cutting guide locator.

FIG. 18 is a fragmentary top view partly in cross-section, of thefemoral cutting block assembly affixed to the femur.

FIG. 19 is a fragmentary semi-diagrammatic view showing the four femoralcuts.

FIG. 20 is a fragmentary perspective view illustrating the femoralcutting block assembly in place for the femoral cuts.

FIG. 21 is a fragmentary perspective view illustrating the use of thefemoral drill guide.

FIG. 22 is a fragmentary perspective view illustrating the placement ofa trial femoral component.

FIG. 23 is a fragmentary elevational view of the tibial intramedullaryrod of the present invention.

FIG. 24 is a plan view of the vertical tibial cutting block of thepresent invention.

FIG. 25 is a side elevational view, partly in cross-section, of thevertical tibial cutting block of FIG. 24.

FIG. 26 is a fragmentary plan view of the tibial marking/drillingtemplate assembly of the present invention.

FIG. 27 is a side view of the tibial marking/drilling template assemblyof FIG. 26.

FIG. 28 is an elevational view of the horizontal tibial cutting guide ofthe present invention.

FIG. 29 is a side view of the horizontal tibial cutting guide, partly incross-section, as seen from the left of FIG. 28.

FIG. 30 is an elevational view of the caliper measuring device of thepresent invention

FIG. 31 is a fragmentary cross-sectional view taken along section line31--31 of FIG. 30.

FIG. 32 is a fragmentary perspective view illustrating the drilling ofthe tibia for the tibial intramedullary rod.

FIG. 33 is a fragmentary perspective view illustrating the placement ofthe tibial intramedullary rod.

FIG. 34 is a fragmentary perspective view illustrating the use of thetibial marking/drilling template assembly to determine the size of thevertical tibial cutting block to use.

FIG. 35 is a fragmentary perspective view illustrating the mounting ofthe tibial vertical cutting block of FIGS. 24 and 25.

FIG. 36 is a fragmentary perspective view illustrating the horizontaltibial cutting guide and the horizontal tibial cut being made.

FIG. 37 is a fragmentary perspective view illustrating the use of thevertical tibial cutting block in making the vertical tibial cut.

FIG. 38 is a fragmentary perspective view illustrating the use of thetibial marking/drilling template assembly for drilling in preparationfor the fixation of the tibial tray.

FIG. 39 is a fragmentary perspective view illustrating the fixation ofthe tibial tray.

FIG. 40 is a fragmentary perspective view, similar to FIG. 37,illustrating the tibial insert mounted in the tibial tray.

FIG. 41 is a fragmentary perspective view illustrating both the femoraland tibial components in place.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of clarity, the instruments used in the preparation of thedistal femur, and the preparation of the distal femur, will first bedescribed. This will be followed by a description of the instrumentsused in the preparation of the proximal tibia and the preparation of theproximal tibia, itself. In all of the figures, like parts have beengiven like index numerals.

FIGS. 1 and 2 illustrate the femoral template of the present invention.The femoral template is generally indicated at 1 and comprises arelatively thin, stainless steel, planar member. The femoral template 1has a handle portion 2 and a head portion 3. The head 3 has asubstantially arcuate measuring surface or edge 4 terminating inposterior and anterior ends 5 and 6, respectively. The template 1 can beused on either the medial or the lateral condyle, of either the left orthe right knee. The template 1 is provided in three sizes: small,standard and large.

The femoral intramedullary rod (hereinafter referred to as the femoralIM rod) is generally indicated at 7 in FIGS. 3 and 4. The femoral IM rodcomprises an elongated, rod-like shank 8 having at its lower end atapered portion 9 terminating in a rounded point 10. At its upper end,there is permanently affixed to the femoral IM rod a head 11 havingparallel planar sides 11a and 11b and rounded ends 11c and 11d. The head11 and the adjacent uppermost end of the femoral IM rod are providedwith a threaded bore 12, adapted to receive a bolt 13 provided with ahead engageable by a socket wrench. It will be noted that the head 11,the axis of the central bore 12 therein and the axis of bolt 13 areangularly related to the long axis of the shank 8. The femoral IM rod ismade in three substantially identical versions, differing only in thatthe above noted angular relationship is respectively 3°, 5° and 7°. Thechoice of the appropriate femoral rod to use, will depend upon thevalgus orientation of the patient's femoral anatomy. The femoral IM rodassembly, including the bolt 13, is made of stainless steel.

FIGS. 5 and 10 illustrate the femoral cutting block locator, generallyindicated at 14. This instrument comprises an elongated handle 15, aportion 16 of which may be knurled to assure a secure grip by the handof the surgeon. The handle 15 supports at one end a U-shaped member 17having a base portion 18 terminating in a long leg 19 and a short leg20. The short leg 20 is slightly thinner than the remainder of theU-shaped member 17 so that it can be received in a posterior cuttingslot of the femoral cutting block (see FIG. 10), as will be apparenthereinafter. The femoral cutting guide locator is also made of stainlesssteel.

The femoral cutting block is generally indicated at 21 in FIGS. 6 and 7.The femoral cutting block 21 comprises an L-shaped member having a longleg 22 and a short leg 23. The long leg 22 is provided with a superiorslot 24 for making the posterior chamfer cut and an inferior slot 25 formaking the anterior chamfer cut. Below slot 25 there is a slot 26 formaking the posterior surface cut. Finally, the short leg 23 is providedwith a distal femoral articular surface cutting slot 27.

Substantially centrally of the sides of the long leg 22, the femoralcutting block has a pair of slotted lug assemblies 28 and 29. As will beapparent hereinafter, these slotted lug assemblies permit the attachmentof the femoral IM rod and the femoral outrigger to the cutting block 21.Immediately behind the lug assemblies 28 and 29, the rear surface of thecutting block 21 is provided with recesses 30 and 31, respectively,which further serve to accommodate the femoral IM rod and the outrigger,as will be explained hereinafter. The femoral cutting block can be usedwith either femoral condyle of either leg of the patient. It is providedin three sizes: small, standard and large, and is made of stainlesssteel.

FIGS. 8 and 9 illustrate the femoral outrigger of the present invention.The femoral outrigger is generally indicated at 32 and comprises anL-shaped, plate-like member having a long leg 33 and a short leg 34. Theshort leg 34 is thicker than the long leg 33 and is provided with acentral threaded bore 34a (see FIG. 10) adapted to receive a bolt 35similar to the bolt 13 of the femoral IM rod (see FIG. 3). The bolt 35is provided with a head adapted to be engaged by a socket wrench.

The short leg 34 is provided with a second threaded bore (not shown). Ahandle or alignment bar 36 is threadedly engaged in the last mentionedbore and extends perpendicularly to the outside face of long leg 32.Finally, the long leg 32 is provided with four perforations 37, thepurpose of which will be apparent hereinafter. The femoral outrigger andits appurtenances are made of stainless steel

FIG. 10 is an exploded view illustrating the entire femoral cuttingguide assembly. It will be apparent from FIG. 10 that the femoral IM rod7 can be affixed to either side of femoral cutting block 21. In thisinstance, the shank of bolt 13 is received in the slotted lug assembly28 and the head 11 of the femoral IM rod will be received in the recess30 (see FIG. 6) of the femoral cutting block 21. It will similarly beapparent that the outrigger 32 could be attached to either side of thefemoral cutting block 21. In this instance, the short leg 34 ofoutrigger 32 is received within the cutting block recess 31 and the bolt35, threadedly engaged in the outrigger perforation 34a is received inthe slotted lug assembly 29. The slotted lug assemblies 28 and 29 permitadjustment between the femoral IM rod 7, the femoral outrigger 32, andthe femoral cutting block 21. Finally, it is evident that the upper leg20 of the femoral cutting guide locator can be received in the slot 26of the femoral cutting block 21.

FIG. 11 illustrates the femoral drill guide of the present invention.This instrument is generally indicated at 38, is made of stainlesssteel, and comprises an elongated shank 39 terminating at one end in aknurled handle 40. The other end of shank 39 supports a drill guidetemplate 41. The template 41 comprises a plate-like member terminatingat its free end in a rearwardly extending flange 42 (see also FIG. 21).The template 41 has an inferior drill guide bore 43 and a superior drillguide bore 44, the purposes of which will be apparent hereinafter. Thefemoral drill guide is provided in small, standard and large sizes.

The final specialized instrument for use in the preparation of thefemoral condyle is an IM rod removal tool, generally indicated at 45 inFIG. 12. The IM rod removal tool 45, made of stainless steel, comprisesan elongated rod-like shank 46 terminating at one end in a handleelement 47 which is threadedly engaged thereon. The other end of shank45 is provided with a bifurcated claw element 48. Slidably mounted onthe shank 46, between the handle element 47 and the claw element 48there is an impact element 49. The surgeon can cause the impact member49 to hammer against the handle element 47 so that the IM rod removaltool 45 serves as an extracting tool.

The primary instruments involved having been described, the method forpreparing the distal femur to receive the distal femoral prosthesis willnow be set forth. For purposes of an exemplary showing, the totalreplacement of the medial condyle of a patient's right leg will bedescribed. A medial femoral condyle is chosen simply because a medialcondyle is more likely to become diseased than a lateral condyle, sincethe medial condyle bears more of the patient's weight. It will beunderstood that the steps involved in the treatment of the medialcondyle of a patient's right leg would be substantially identical tothose involved in the treatment of the lateral condyle of a patient'sleft leg. Replacement of the lateral condyle of the right leg or themedial condyle of the left leg would differ only in the use of left handinstruments rather than right hand instruments in those instances whereinstruments are provided in both left hand and right hand forms, and ininstrument placement, as will be apparent hereinafter.

The first step in the procedure, of course, is the surgical exposure ofthe distal end of the femur and the proximal end of the tibia Thesurgical procedures for this are well known in the art and do notconstitute a part of the present invention.

In FIG. 13, the distal end of the femur is generally indicated at 50 andthe proximal end of the tibia is generally indicated at 51. The medialcondyle to be treated is shown at 52. As a first step, an appropriatelysized femoral template 1 has its measuring edge or surface 4 locatedagainst condyle 52 to determine the appropriate size (small, standard orlarge) of the femoral cutting block to be used.

Once this has been determined, an appropriately sized hole 53 is made,utilizing a surgical drill 54, immediately above the intercondylar notch55. It will be assumed, for purposes of this description, that astandard sized femoral template was selected, as well as a 5° femoral IMrod. The tapered end of the rod is introduced into the drilled hole 53.The femoral IM rod 7 is driven down the femoral shaft. This is shown inFIG. 15.

With the femoral IM rod 7 in place, a standard femoral cutting block 21is mounted thereon, by engaging the femoral IM rod bolt 13 in theslotted lug assembly 28 of the cutting block. At this stage, the bolt 13is not fully tightened, and the slotted lug assembly 28 will permitshifting of the femoral cutting block 21 to achieve its properplacement. FIG. 16 illustrates the femoral cutting block 21 attached tothe femoral IM rod 7.

Next, the femoral cutting guide locator 14 has its short leg 20 insertedin the posterior surface cutting slot 26. The long leg 19 of the femoralcutting guide locator 14 contacts the posterior condyle to make certainthat the position of the femoral cutting block 21 is appropriate in theanterior posterior plane. This is illustrated in FIG. 17.

As is shown in FIGS. 18 and 20, the femoral outrigger 32 is thereafteraffixed to the femoral cutting block 21 by engaging the outrigger bolt35 in the slotted lug assembly 29 of cutting block 21. The bolt 35 isfully tightened with the use of a socket wrench. Thereafter, rotationalalignment of the axial plane is checked, using the rotational alignmentbar or handle 36 on outrigger 32. When properly positioned, this handleor alignment bar 36 should be perpendicular to the shaft of the tibia.

When the femoral cutting block 21 is properly positioned and is flushwith the distal femoral condylar surface, the outrigger 32 is fixed tothe femur utilizing up to 4 smooth pins 37a impacted firmly into thefemoral bone through any of the holes 37 of outrigger 32. The femoral IMrod bolt 13 is then firmly tightened. As a result of the above-notedsteps, the femoral cutting block 21 demonstrates excellent stabilitysince it is affixed to the femur itself.

At this point, the surgeon is ready to make the four bony cuts, asindicated in FIG. 20 by the surgical saw 56. In FIGS. 19 and 20, thebroken line A represents the superior posterior chamfer cut. The brokenline B indicates the inferior anterior chamfer cut. The broken line Cindicates the postarticular surface cut and the broken line D designatesthe distal femoral articular surface cut. These cuts can be made in anyorder.

Once the four cuts have been made, the outrigger 32 is removed bypulling pins 37a and loosening bolt 35. The cutting block 21 isthereafter removed from the femoral IM rod 7 by loosening bolt 13.Thereafter, the femoral IM rod, itself, is removed by engaging thebifurcated claw element 48 of impacter-disimpacter instrument 45 beneathits head 11 and causing the impact element 49 of the instrument 45 toapply blows to its handle element 47.

With the outrigger 32, femoral cutting block 21 and femoral IM rod 7removed, the template element 41 of the femoral drill guide 38 is laidalong the new surface produced by the distal femoral articular surfacecut D. The rearwardly extending flange 42 of template 41 engages the newsurface produced by the postarticular cut C. An appropriately sizeddrill bit 57 is introduced into the drill guide inferior bore 43 and ahole 58 is drilled in the surface created by cut D. A smooth pin 59 isinserted in the drill guide inferior bore 43 and is pounded firmly intobore 58 The drill bit 57 is then introduced into the drill guidesuperior bore 44 and a second hole 60 is drilled in the surface formedby cut D.

With the holes 58 and 60 drilled, the pin 59 is removed, as is thefemoral drill guide 38. At this stage, preparation of the femoralcondyle is complete. A metal trial component 61, provided with mountingpegs 62 and 63 may be applied to the prepared condyle to assure a closeapproximation of the opposed component and condyle surfaces. To thisend, mounting peg 62 is inserted in hole 58 and mounting peg 63 isinserted in hole 60, the trial component is then driven to a fullyseated position by an appropriate tool 64.

The instrumentation used for preparing the proximal tibia to receive theproximal tibial prosthesis is illustrated in FIGS. 23-30.

Turning first to FIG. 23, the tibial intramedullary rod (hereinafterreferred to as the tibial IM rod) is generally indicated at 65. The rodhas an elongated shank 66 of circular cross-section. The lower end ofthe shank 66 is tapered as at 67, terminating in a rounded point 68.Just below its upper end, the tibial IM rod is provided with an annularnotch 69 so sized as to receive the bifurcated claw element of a tibialIM rod removal tool similar to the tool 45 of FIG. 12. The tibial IM rod65 is made of stainless steel.

FIGS. 24 and 25 illustrate the vertical tibial cutting block, generallyindicated at 70. The tibial cutting block 70 has vertical planar sides71 and 72 together with vertical planar forward and rearward surfaces 73and 74. The rearward corners are rounded as at 75 and 76.

The tibial cutting block 70 has planar parallel top and bottom surfaces77 and 78. Centrally of the tibial cutting block 70 there is a verticalbore 79 so sized that it receives the tibial IM rod 65 with a slidingfit. A horizontal threaded bore 80 extends inwardly from the forwardsurface 73 and intersects the bore 79. The bore 80 receives a set screw81 provided with a knob 82. The forward face of the knob 82 is providedwith a socket 83 (see FIG. 33) for receipt of an Allen wrench.

The vertical tibial cutting block 70 and its set screw 81 are made ofstainless steel. The vertical tibial cutting block is made in fivepredetermined sizes wherein the distance between the vertical sides 71and 72 and the bore 79 is 4 mm, 6 mm, 8 mm, 10 mm and 12 mm,respectively.

FIGS. 26 and 27 illustrate the stainless steel instrument comprising thetibial marking/drilling template assembly. The tibial marking/drillingtemplate assembly is generally indicated at 84. The instrument comprisesan elongated handle 85 having a central knurled portion 86. At one end,the handle 85 supports a right marking/drilling template 87. At theother end, the handle supports a left marking/drilling template 88.

The right template 87 comprises a planar member. The left side 89 of theright template 87 is rectilinear. The right side 90 of the righttemplate approximates the shape of the medial edge of the right side ofthe tibial prosthesis. The template 87 is provided with a pair of pins91 and 92 which are essentially flush with or slightly countersunk withrespect to the upper surface of the template. The pins 91 and 92 havepointed lower ends which extend slightly below the bottom surface of thetemplate 87.

The right template 87 has a pair of substantially identical medial andanterior drill guide bores 93 and 94, the purpose of which will beapparent hereinafter. Finally, the right template is provided with asloping bore 95 which receives a tubular drill bit guide 96 The drillbit guide 96 is flush with the bottom surface of the template andextends upwardly from the upper surface of the template.

The left template 88 is essentially a mirror image of the right template87, having a rectilinear edge 97 equivalent to the rectilinear edge 89and an arcuate edge 98 equivalent to the arcuate edge 90. The lefttemplate 88 has a pair of medial and anterior drill bit guide bores 99and 100 equivalent to drill bit guide bores 93 and 94 respectively.Similarly, the left template 88 is provided with pins 101 and 102identical to pins 91 and 92. Finally, left template 88 is provided witha sloping bore 103 equivalent to bore 95 and provided with a tubulardrill bit guide 104 equivalent to the drill bit guide 96.

When the medial condyle of the right leg or the lateral condyle of theleft leg is diseased, the right template 87 of instrument 84 will beused. When the medial condyle of the left leg or the lateral condyle ofthe right leg is diseased, the left template 88 of instrument 84 will beused. The instrument 84 is provided in three sizes: a first having smallright and left templates 87 and 88, a second having standard right andleft templates 87 and 88, and a third having large right and lefttemplates 87 and 88.

The stainless steel horizontal tibial cutting guide is illustrated inFIGS. 28 and 29 and is generally indicated at 105. The horizontal tibialcutting guide 105 comprises a vertically oriented sleeve 106 having abore 107 adapted to receive the tibial IM rod with a sliding fit. Thesleeve 106 is provided with a set screw 108, terminating in a knob 109.The knob 109 can be operated manually, and is additionally provided inits front face with a socket 110 for receipt of an Allen wrench. Bymeans of set screw 108, the horizontal tibial cutting guide 105 can belocked in any desired vertical and radial position with respect to thetibial IM rod.

The sleeve 106 supports a laterally extending bar 111 of squarecross-section. The upper surface of bar 111 is provided with alongitudinally extending notch 112. Mounted on bar 111 there is a collar113 provided with a square longitudinal bore 114. The collar islongitudinally shiftable on bar 111 Collar 113 is provided with a setscrew 115 terminating in a knob 116 similar to knob 109. The knob 116 isprovided in its front face with a socket 117 for receipt of an Allenwrench.

The collar 113 has an integral downwardly depending portion 118 to whichthe cutting platform 119 is adjustably affixed by a button head capscrew 120 to allow a swiveling action.

The cutting platform 119 has an arcuate surface 121 adapted to face andabut the anterior tibial surface on the operative side. The cuttingplatform 119 has a pair of cutting guide slots 122 and 123 so that thehorizontal tibial cutting guide can be used with respect to eithertibial compartment of either leg. The horizontal tibial cutting guide iscompleted by providing the cutting platform with four holes 124. Theseholes are adapted to receive smooth pins by which the cutting platformcan be temporarily firmly affixed to the tibia, as will be describedhereinafter.

FIGS. 30 and 31 illustrate the stainless steel caliper measuring deviceof the present invention, generally indicated at 125. The calipermeasuring device comprises a vertically oriented caliper rod 126. Thecaliper rod 126 has a longitudinally extending planar surface 127containing measurement indicia. The caliper rod 126 is slidably mountedin a caliper sleeve 128. Button-like elements 129 and 130 are affixed tothe ends of the caliper rod rendering it captive within caliper sleeve128.

The caliper sleeve 128 is affixed to one end of a support rod 131. Thesupport rod 131, in turn, is slidably received in a horizontaltransverse bore 132 in caliper block 133. Thus, the caliper sleeve 128and caliper rod 126 can be shifted toward and away from caliper block133.

Caliper block 133 has a vertical bore 134 adapted to slidably receivethe tibial IM rod 65. It will be noted from FIG. 31 that the horizontaltransverse bore 132 for the caliper sleeve support rod 131 intersectsthe vertical bore 134. The bore 134 is also intersected by a horizontalthreaded bore 135 mounting a set screw 136 provided with a knob 137. Theknob 137 can be manipulated by hand and is also provided with aforwardly facing socket 138 for the receipt of an Allen wrench.

From the above description, it will be apparent that the caliper rod 126can not only be shifted toward and away from caliper block 133, but alsocan be rotated about the tibial IM rod 65. Furthermore, the calipersleeve support rod 131 can be shifted vertically along the tibial IM rod65. When the caliper rod 126 is positioned as desired, and the upperedge of the caliper sleeve is located adjacent the desired measurementindicia on flat 127, the knob 137 can be tightened. It will be evidentfrom FIG. 31 that the knob 137 will lock both the tibial IM rod 65 andthe caliper sleeve support rod 131 within the caliper block 133.

The vertical tibial cutting block 70, the horizontal tibial cuttingguide 105, the caliper measuring device 125 and the tibial IM rod 65constitute a tibial cutting guide assembly, as will be apparent.

The primary instruments used in the preparation of the tibialcompartment having been described, the steps involved in the tibialcompartment preparation can now be set forth. Again, like parts havebeen given like index numerals.

FIG. 32 illustrates the first step in the preparation of the tibialcompartment. A hole (indicated in broken lines at 139 is drilled bysurgical drill 140 for placement of the tibial IM rod 65. The hole 139is so located as to avoid the anterior cruciate ligament insertion inthe tibial plateau. The cruciate ligament is shown at 141 in FIG. 32.

The tibial IM rod is then impacted through hole 139 and down the tibialshaft, with care being taken to avoid varus or valgus angulation of thetibial IM rod during impaction. FIG. 33 illustrates the tibular IM rod65 in place. It will be noted that more than 50% of the tibular IM rodhas been driven into the tibial shaft.

A natural 5° posterior inclination of the tibial IM rod will result dueto the anterior placement of the tibial IM rod to avoid injuring theanterior cruciate ligament. This 5° posterior tilt of the tibial IM rodwill be accommodated by the horizontal tibial cutting guide 105 of FIGS.28 and 29. It will be noted in FIG. 29 that the cutting guide slots 22and 23 slope slightly to make up for the posterior tilt of the tibial IMrod.

Reference is now made to FIG. 34. With the tibial IM rod 65 in place,the appropriate template (in this instance the right template 87) of anappropriately sized tibial marking/drilling template assembly 84 isplaced on the tibial plateau with its arcuate edge 90 placed flush withthe medial edge of the tibial cortex. The distance E between the tibialIM rod and the rectilinear edge 89 of the tibial marking/drillingtemplate assembly is marked, directly on the tibia utilizing a cuttingcautery. Such a mark is shown in FIG. 34 at 141. Once the mark 141 hasbeen made, the tibial marking/drilling template assembly is removed. Thedistance E is used to select the appropriately sized tibial cuttingblock (see FIGS. 24 and 25). If the distance E, for example, isapproximately 8 mm, then an 8 mm tibial cutting block is selected. As isshown in FIG. 35, the appropriately sized vertical tibial cutting block70 is mounted on the tibial IM rod 65 and located flush with the cortexof the tibia. At this point, the set screw 81 of the tibial cuttingblock 70 is tightened by insertion of an Allen wrench (not shown) intothe socket 83 of knob 82.

The next series of steps are illustrated in FIG. 36. With the verticaltibial cutting block 70 in place, the horizontal tibial cutting guide isnext mounted by placing its sleeve 106 over the tibular IM rod 65. Ifrequired, the collar 113 may be adjusted by knob 116 so that the cuttingplatform 119 can be properly positioned with respect to the tibia. Thecutting platform 119 can also be rotated horizontally about the tibialIM rod 65 to achieve its proper position since the sleeve knob 109 hasnot yet been tightened. Thus, the horizontal tibial cutting guide isfully adjustable, capable of being rotated about the tibial IM rod andshifted both vertically and horizontally to bring the cutting platform119 in proper position against the anterior tibial surface on theoperative side. With the horizontal tibial cutting guide 105 still looseon the tibular IM rod 65, the caliper measuring device 125 is located inplace by causing the tibular IM rod 65 to extend upwardly through theperforation 134 in caliper block 133. By appropriate rotation of thecaliper block 133 about the tibular IM rod 65 and by appropriateadjustment of the caliper sleeve supporting rod 131 in caliper blockbore 132 the caliper rod 126 is so located that its bottom end 130contacts the central, most depressed, portion of the tibial plateau. Thecaliper sleeve 128 is raised or lowered (as required) until its upperedge aligns with the 8 mm mark on the caliper rod flat 127. The use ofthe 8 mm mark is preferred so that the least amount of bone is removedfrom the medial tibial compartment. If the tibial plateau is so damagedthat more bone must be removed, the upper edge of the caliper sleeve 128is aligned with the 10 mm or the 12 mm mark. The 8 mm, 10 mm and 12 mmmarks correspond to the relative location of the cutting platform 119and correlate with the overall thickness of the tibial tray to bemounted on the plateau and the three sizes of inserts available for usewith the tibial tray.

It will be understood that as the vertical position of the calipersleeve 128 is adjusted to the surgeon's satisfaction, a similaradjustment of the caliper block 133 with respect to the tibial IM rodwill simultaneously be made. When adjustments are completed, the caliperblock knob 137 is tightened with an Allen wrench 142, locking thecaliper block 133 in position on the tibular IM rod 65.

At this stage, the final adjustment of the tibial horizontal cuttingguide can be made by simply shifting the horizontal cutting guide sleeve106 upwardly on the tibial IM rod 65 until its upper end abut the lowerend of caliper block 133. At this point, the knob 109 is tightened withan Allen wrench to lock the tibial horizontal cutting guide in finalposition. A pair of smooth pins 143 are impacted into the tibia throughtwo of the perforations 124 of the cutting platform 119.

At this point, the instrumentation is ready for the horizontal tibialcut to be made. Since, in the example described, the medial tibialcompartment is being prepared, the cut is made by inserting a surgicalsaw 144 through the guide slot 123 of cutting platform 119.

With the horizontal tibial cut completed, the caliper measuring device125 is removed from the tibial IM rod 65 by loosening knob 137.Thereafter, the pins 143 extending through the cutting platform 119 areremoved. At this point, the knob 109 is loosened, and the horizontaltibial cutting guide 105 is removed from the tibial IM rod 65.

With the caliper measuring device 125 and the horizontal tibial cuttingguide 105 removed, the surgeon is now free to make the vertical tibialcut, as illustrated in FIG. 37. To this end, an appropriatereciprocating surgical saw 145 is located with its blade flush againstthe appropriate side surface of vertical tibial cutting block 70. InFIG. 37, the horizontal cut is indicated by broken line 146. Thevertical cut is indicated at 147. When both the vertical and horizontalcuts have been completed, the bony segment 148 is removed. The verticaltibial cutting block 70 and the tibial IM rod 65 are removed. Uponremoval of the bony part 147, the tibial marking/drilling templateassembly 84 (again of the proper size) has its right template 87 placedover the cut tibial surface with its arcuate side 90 again flush withthe medial edge of the tibial cortex and its rectilinear side 89abutting the vertical cut 147. The template 87 is impacted to assurethat its small pins 91 and 92 imbed in the cut bone surface forstability. Thereafter, an oblique drill hole is made by means of asurgical drill 149, utilizing the angled tubular drill bit guide 96. Theoblique drill hole is made to receive the tibial tray peg. Anothersurgical drill 150 is used to drill a hole through the medial templatehole 93, aligning the drill to penetrate the cortex medially. The drill150 is thereafter used to drill a hole through the anterior templatedrill guide hole 92. This anterior drill hole is made vertically, orangled anteriorly if cortical fixation by the screw is preferred.

At this point, a tibial tray 151 is selected, identical in size to thetemplate 87. The tibial tray 151 is located on the cut tibial surfacewith the peg (not shown) of the tibial tray located in the oblique holemade by drill 149. The tibial tray 151 is impacted in place. Thereafter,screws 152 and 153 are located in countersunk holes 154 and 155 in thetibial tray and screwed into the medial and anterior drill holes made bysurgical drill 150. The heads of screws 152 and 153 will be flush withthe upper bottom surface of the tibial tray 151.

At this point, a black plastic, slightly undersized, tibial trialimplant can be placed within the tibial tray 146. The tibial tray andtrial implant should correlate with the amount of bone removed, asdetermined by the caliper measuring device 125 at the time of the tibialresection. The trial femoral component can then also be placed on thefemur. In mild flexion there should be approximately a 2 mm to 3 mm gapbetween the components with valgus stress. Thereafter, the trialcomponents are removed and the appropriate height polyethylene tibialinsert 15 is impacted in place in the tibial tray 151, as shown in FIG.40. The permanent femoral component 153 is then appropriately mounted asshown in FIG. 41. Tracking is noted throughout full flexion andextension. At this stage, the replacement procedure is complete. Closingand postoperative procedures are substantially conventional and do notconstitute a part of the present invention.

From the above description it will be apparent that the sameinstrumentation can be used when the lateral tibial compartment is to betreated. The mounting of the tibial IM rod is identical. Selection of anappropriately sized vertical tibial cutting guide is made in the samemanner using the left template 88 of the tibial marking/drillingtemplate assembly 84. The use of the horizontal tibial cutting guide 105and the caliper measuring device 125 is the same, the caliper block 133being rotated on the tibial IM rod so that the caliper rod cooperateswith lateral tibial plateau. The horizontal and vertical tibial cuts aremade using the slot 122 of the cutting guide 119 and using theappropriate side of the vertical cutting block 70. The holes are drilledin the horizontal cut surface of the tibia using the left template ofinstrument 84. Thereafter, an appropriately sized lateral tibial trayand insert are installed.

It is within the scope of the invention to glue the femoral and tibialcomponents in place. When the tibial tray 151 is glued in place, screws152 and 153 might not be used. The holes 154 and 155 in the tibial trayare provided with plastic plugs to prevent glue from entering that partof the tibial tray in which insert 152 is mounted.

Modifications may be made in the invention without departing from thespirit of it.

What is claimed is:
 1. A tibial cutting guide assembly for use inreplacing the articulating tibial surface of a knee joint in which thediseased area is restricted to the femoral condyle and tibial plateau ofone of the medial and lateral compartments, said tibial cutting guideassembly comprising a tibial IM rod, a vertical tibial cutting block, ahorizontal tibial cutting guide and a caliper measuring device, saidtibial IM rod being of such length as to be insertable down the centerof the tibia with a free end exposed, said vertical tibial cutting blockcomprising a block-like member having parallel planar sides constitutingvertical medial and lateral cutting guides and a vertical hole sized toreceive said free end of said tibial IM rod, said vertical tibialcutting block being vertically shiftable along and rotatable about saidfree end of said IM rod, said vertical tibial cutting block having a setscrew intersecting said hole therein for locking said vertical tibialcutting block in adjusted position on said tibial IM rod free end, saidhorizontal tibial cutting guide comprising a sleeve having a bore sizedto receive said free end of said tibial IM rod and being slidable androtatable thereon, said sleeve having a set screw intersecting said borefor locking said sleeve in adjusted position on said tibial IM rod freeend above said vertical tibial cutting block, a cutting platform, meanson said sleeve for adjustably supporting said cutting platform formovement toward and away from the tibia, said cutting platform having anarcuate portion facing said tibia and having medial and lateral surgicalsaw blade guide slots extending inwardly from each end thereof formaking horizontal tibial cuts in either compartment of said knee joint,and means to fasten said arcuate portion directly to the tibia, saidcaliper measuring device comprising a block-like element, said caliperblock having a vertical hole therein so sized as to receive said freeend of said tibial IM rod, said caliper block being vertically shiftablealong and rotatable about said free end of said tibial IM rod above saidhorizontal tibial cutting guide sleeve, said caliper block having atransverse horizontal bore partially intersecting said vertical hole, asupport rod mounted in said horizontal bore and being shiftable axiallytherein, said caliper block having a set screw intersecting saidvertical hole for locking said caliper block in adjusted position onsaid tibial IM rod free end and for locking said support rod in adjustedaxial position in said caliper block, said support rod having a freeend, a vertically oriented caliper sleeve affixed to said support rodfree end, a caliper rod mounted in said vertical caliper sleeve andbeing axially shiftable and captive therein, said caliper sleeve havingan upper end, measurement indicia on said caliper rod cooperating withsaid upper end of said caliper sleeve, said measurement indiciacorresponding to the relative location of said cutting platform.
 2. Thestructure claimed in claim 1 including a laterally extending bar on saidhorizontal tibial cutting guide sleeve, a collar slidably mounted onsaid bar, a set screw mounted in said collar to lock said collar inadjusted position on said bar, said collar having a downwardly dependingportion, said cutting platform being affixed to said downwardlydepending collar portion.
 3. The structure claimed in claim 1 whereinsaid cutting platform is provided with a plurality of holes by which itmay be affixed directly to the tibia with smooth pins.
 4. Femoral andtibial cutting guide assemblies for use in replacing the articulatingfemoral and tibial surfaces of a knee joint in which the diseased areais restricted to the femoral condyle and tibial plateau of one of themedial and lateral compartments, said femoral cutting guide assemblycomprising a femoral cutting block, a femoral IM rod and an outrigger,said femoral cutting block having four-surgical saw blade guide slotstherethrough for making on said diseased condyle a posterior articularcut surface, a distal articular cut surface, a posterior chamfer cutsurface and an anterior chamfer cut surface, said femoral IM rod beingof such length as to be insertable down the center of the femur with afree end exposed, one side of said femoral cutting block beingadjustably affixed to said free end of said femoral IM rod, saidoutrigger comprising a plate-like member adjustably affixed to the otherside of said femoral cutting block, said outrigger having holes thereinfor the receipt of smooth pins by which said outrigger is attachable tosaid femur, said tibial cutting guide assembly comprising a tibial IMrod, a vertical tibial cutting block, a horizontal tibial cutting guideand a caliper measuring device, said tibial IM rod being of such lengthas to be insertable down the center of the tibia with a free endexposed, said vertical tibial cutting block comprising a block-likemember having parallel planar sides constituting vertical medial andlateral cutting guides and a vertical hole sized to receive said freeend of said tibial IM rod, said tibial vertical cutting block beingvertically shiftable along and rotatable about said free end of said IMrod, said vertical tibial cutting block having a set screw intersectingsaid hole therein for locking said vertical tibial cutting block inadjusted position on said tibial IM rod free end, said horizontal tibialcutting guide comprising a sleeve having a bore sized to receive saidfree end of said tibial IM rod and being slidable and rotatable thereon,said sleeve having a set screw intersecting said bore for locking saidsleeve in adjusted position on said tibial IM rod free end above saidvertical tibial cutting bloc, a cutting platform, means on said sleevefor adjustably supporting said cutting platform for movement toward andaway from the tibia, said cutting platform having an arcuate portionfacing said tibia and having a pair of surgical saw blade guide slotsextending inwardly from each end thereof for making horizontal tibialcuts in either compartment of said knee joint, and means to fasten saidarcuate portion directly to the tibia, said caliper measuring devicecomprising a block-like element, said caliper block having a verticalhole therein so sized as to receive said free end of said tibial IM rod,said caliper block being vertically shiftable along and rotatable aboutsaid free end of said tibial IM rod above said horizontal tibial cuttingguide sleeve, said caliper block having a transverse horizontal borepartially intersecting said vertical hole, a support rod mounted in saidhorizontal bore and being shiftable axially therein, said caliper blockhaving a set screw intersecting said vertical hole for locking saidcaliper block in adjusted position on said tibial IM rod free end andfor locking said support rod in adjusted axial position in said caliperblock, said support rod having a free end, a vertically oriented calipersleeve affixed to said support rod free end, a caliper rod mounted insaid vertical caliper sleeve and being axially shiftable and captivetherein, said caliper sleeve having an upper end, measurement indicia onsaid caliper rod cooperating with said upper end of said caliper sleeve,said measurement indicia corresponding to the relative location of saidcutting platform.
 5. The structure claimed in claim 4 wherein saidfemoral cutting block is of inverted L-shaped configuration having along leg and a short leg, said slots for making said posterior articularcut surface and said posterior and anterior chamfer cut surfaces beinglocated in said long leg, said slot for making said distal articular cutsurface being in said short leg.
 6. The structure claimed in claim 5wherein said long leg of said femoral cutting lock has a slotted lug oneither side thereof and a recess behind each of said slotted lugs. 7.The structure claimed in claim 6 wherein said femoral IM rod comprises ashank having a first end with a tapered portion terminating in a roundedpoint and a second end to which a head is affixed, said head having athreaded bore and a bolt mounted in said threaded bore, said head andbolt being angularly related to the long axis of said shank by one of3°, 5° and 7°, said femoral IM rod bolt being receivable in either ofsaid femoral cutting block slotted lugs and said femoral IM rod headbeing partially receivable in either of said femoral cutting blockrecesses whereby either side of said femoral cutting block can beadjustably attached to said femoral IM rod.
 8. The structure claim inclaim 6 wherein said femoral outrigger comprises an inverted L-shapedplate-like member having a short leg and a long leg, said short leghaving a centrally located threaded bore and a bolt threadedly engagedin said bore, said long leg having said holes therein for the receipt Ofsmooth pins, said outrigger bolt being receivable in either of saidfemoral cutting block slotted lugs and said outrigger short leg beingpartially receivable in either of said femoral cutting block recesseswhereby either side of said femoral cutting block can be adjustablyattached to said outrigger.
 9. The structure claimed in claim 4 whereinsaid femoral IM rod comprises a shank having a first end with a taperedportion terminating in a rounded point and a second end to which a headis affixed, said head having a threaded bore and a bolt mounted in saidthreaded bore, said head and bolt being angularly related to the longaxis of said shank by one of 3°, 5° and 7°.
 10. The structure claimed inclaim 4 wherein said femoral outrigger comprises an inverted L-shapedplate-like member having a short leg and a long leg, said short leghaving a centrally located threaded bore and a bolt threadedly engagedin said bore, said long leg having said holes therein for the receipt ofsmooth pins.
 11. The structure claimed in claim 10 wherein saidoutrigger long leg has a planar outside surface facing away from saidcondyle, a rod-like handle/alignment bar being affixed to said outriggerlong leg extending perpendicularly from its outside surface.
 12. Thestructure claimed in claim 4 including a laterally extending bar on saidhorizontal tibial cutting guide sleeve, a collar slidably mounted onsaid bar, a set screw mounted in said collar to lock said collar inadjusted position on said bar, said collar having a downwardly dependingportion, said cutting platform being affixed to said downwardlydepending collar portion.
 13. The structure claimed in claim 4 whereinsaid cutting platform is provided with a plurality of holes by which itmay be affixed directly to the tibia with smooth pins.
 14. A femoralcutting guide assembly for use in replacing the articulating femoralsurface of a knee joint in which the diseased area is restricted to thefemoral condyle and tibial plateau of one of the medial and lateralcompartments, said femoral cutting guide assembly comprising a femoralcutting block, a femoral IM rod and an outrigger, said femoral cuttingclock being of inverted L-shaped configuration having a long leg and ashort leg, said long leg having surgical saw blade guide slotstherethrough for making on said diseased condyle a posterior articularcut surface, a posterior chamfer cut surface and an anterior chamfer cutsurface, said short leg having a surgical saw blade guide slottherethrough for making a distal articular cut surface on said diseasedcondyle, said femoral IM rod being of such length as to be insertabledown the center of the femur with a free end exposed, one side offemoral cutting block being adjustably affixed to said free end of saidfemoral IM rod, said outrigger comprising a plate-like member adjustablyaffixed to the other side of said femoral cutting block said long leg ofsaid femoral cutting block having a slotted lug on either side thereofand a recess behind each of said slotted lugs for said attachment ofsaid femoral IM rod and said outrigger, said outrigger having holestherein for the receipt of smooth pins by which said outrigger isattachable to said femur.
 15. The structure claimed in claim 14 whereinsaid femoral IM rod comprises a shank having a first end with a taperedportion terminating in a rounded point and a second end to which a headis affixed, said head having a threaded bore and a bolt mounted in saidthreaded bore, said head and bolt being angularly related to the longaxis of said shank by one of 3°, 5° and 7°, said femoral receivable ineither of said femoral cutting block slotted lugs and said femoral IMrod head being partially receivable in either of said femoral cuttingblock recesses whereby either side of said femoral cutting block can beadjustably attached to said femoral IM rod.
 16. The structure claimed inclaim 14 wherein said femoral outrigger comprises an inverted L-shapedplate-like member having a short leg and a long leg, said short leghaving a centrally located threaded bore and a bolt threadedly engagedin said bore, said long leg having said holes therein for the receipt ofsmooth pins, said outrigger bolt being receivable in either of saidfemoral cutting block slotted lugs and said outrigger short leg beingpartially receivable in either of said femoral cutting block recesseswhereby either side of said femoral cutting block can be adjustablyattached to said outrigger.
 17. A horizontal tibial cutting guide foruse in unicompartmental total knee arthroplasty, said horizontal tibialcutting guide comprising a vertical sleeve, a bar extending laterallyfrom said sleeve, a collar slidably mounted on said bar, a set screwmounted in said collar to lock said collar in adjusted position on saidbar, said collar having a downwardly depending portion, a cuttingplatform affixed to said downwardly depending collar portion, saidcutting platform having an arcuate portion for abutment against a tibia,said cutting platform having medial and lateral surgical saw blade guideslots extending inwardly from each end thereof for making horizontaltibial cuts in either compartment of a knee joint, a plurality ofperforations in said cutting platform for the fastening thereof directlyto a tibia by smooth pins, said sleeve having a vertical boretherethrough and a set screw intersecting said bore whereby saidhorizontal cutting guide can be mounted on a tibial IM rod with bothvertical and rotational adjustability and can be fixed thereon inadjusted position.
 18. A caliper measuring device for use inunicompartmental total knee arthroplasty, said caliper measuring devicecomprising a block-like element, said caliper block having a verticalhole therein sized to receive a tibial IM rod with a sliding fit so asto be vertically and rotationally adjustable with respect thereto, saidcaliper block having a transverse horizontal bore partially intersectingsaid vertical hole, a support rod mounted in said horizontal bore andbeing shiftable axially therein, said caliper block having a set screwintersecting said vertical hole for locking said caliper block inadjusted position with respect to a tibial IM rod and locking saidhorizontal support rod in adjusted axial position in said caliper block,said horizontal support rod having a free end, a vertically orientedcaliper sleeve affixed to said horizontal support rod free end, avertically oriented caliper rod slidably and captively mounted in saidcaliper sleeve, said caliper sleeve having an upper end, measurementindicia on said caliper rod cooperating with said caliper sleeve upperend, said measurement indicia corresponding to the relative location ofsaid cutting platform.
 19. A tibial template assembly for use inunicompartmental total knee arthroplasty comprising a handle terminatingat its ends in right and left mirror image tibial templates, saidtemplates each having upper and lower surfaces, a rectilinear sidesurface and an arcuate side surface approximately the shape of thetibial cortex, each template having a pair of short pointed pinsextending downwardly from its lower surface and an obliquely orientedtubular surgical drill bit guide extending through said template, saidtubular guide extending upwardly from said template upper surface andbeing flush with said template lower surface, whereby said tibialtemplate assembly can be used to locate and drill a hole in either themedial or lateral horizontal tibial cut surface for receipt of a tibialtray mounting peg.
 20. The structure claimed in claim 19 wherein each ofsaid templates has a medial and an anterior surgical drill bit guidehole therein whereby holes can be drilled in the horizontal tibial cutsurface for additionally mounting a tibial tray with screws.
 21. Afemoral cutting block for use in unicompartmental total kneearthroplasty comprising an inverted L-shaped member having a long legand a short leg, said long having slots therethrough comprising surgicalsaw blade guides for the condylar posterior articular cut and thecondylar posterior and anterior chamfer cuts, said short leg having asurgical saw blade guide slot therethrough for making the condylardistal articular cut, a slotted mounted lug extending laterally fromeither side of said long leg, and a recess formed in said long legbehind each slotted mounting lug.